Split existing vB5 installation into two subdomains

[ndoktoruser]

Hello!

I am trying to split one existing vBulletin installation into two subdomains. Is this even possible?

Lets say there are two different sudomains:

forum1.mywebpage.com
forum2.mywebpage.com

In my vBulletin installation I have various subforums:

Subforum A
Subforum B
Subforum C
Subforum D

I would like to have Subforums A and B to be only visible on forum1.mywebpage.com and Subforums C and D only visible on forum2.mywebpage.com

Solutions that come to my mind:

1) One vBulletin installation which checks $_SERVER['HTTP_HOST'] and delivers the correct subforums.

Probably there would be problems with search queries. It would be hard to separate most of the functionalities and it would be hard to find every single place VB does the treatment to fetch data from DB.

2) Two different vBulletin installations with a shared database.
The two installations would have their own database, just userdata would be stored in a shared database. Would this be possible?
Could vBulletin be configured in a way so that it will store userdata in a different database?

Right now I tend towards a shared database, but not sure if this is even possible.

Maybe you know more? Any help is greatly appreciated! Thank you very much.